Using all the gizmos while driving in the snow
Lots of good info here, and perhaps I can summarize for those who don't want to have to think about the technology:
*Switch to AWD if you have the multimode system of the V6s. If you want, you can leave it in this mode all winter. Other than that, no need to fiddle with the gizmos at all.
*Drive as smoothly as possible and think ahead (these two strategies are closely related!)
*If you get the yellow light flashing in the dash, this lets you know the system is taking some action on your behalf, and this suggests there is some significant slipping going on. If you're just motoring along and not aware of any problems, ask yourself if you should slow down. You may also hear some clicking or chattering when the system is working.
*If the system beeps at you, it's complaining that it can't get the vehicle to go the direction you want. Unless you're deliberately trying to throw the vehicle around for fun or otherwise get it out of shape, it may be time to back off. Or it may already be too late!
*The system works when you're in reverse, too. The 4Runner's wheel sensors are one of the few that can tell which direction the wheels are turning, and are active/accurate down to speeds like 0.1 MPH or so.
[This applies to the current generation 4Runners; I can't speak for the rest]
A few details:
The 4Runner system (stability control, traction control, throttle-by-wire, antilock brakes, electronic brakeforce distribution, brake assist, Torsen center differential, etc.) is an excellent one, though a bit conservative. That's why there's generally no need to do anything but put the vehicle in 4WD and pay attention to blinking lights or beepers. And drive carefully, of course.
Practice on a slick surface (snowy parking lot or hill) is fun and enlightening, but not essential. The system is designed so that it doesn't require your understanding or active intervention. BTW, I don't think there is a significant benefit to shifting out of D, but perhaps a lower gear would make long downhills a little easier
If you're bashing ahead through deep snow and beginning to lose momentum (especially if you think it's because of de-throttling), you can try locking the differential. Spinning tires (normally prevented by traction control) can be helpful in deep snow or mud.